Twenty-four compounds of this class have been isolated from root or stem bark of neem
(Table I). These chiefly belong to two groups, podacarpanoids and abietanoids. Sugiol (1,
12-hydroxy-13-methy1-podacarpa-8,11,13-trien-7-one) and nimbiol (4, 12-hydroxy-abieta-8,
11, 13-¬trien-7-one) were the first members of the respective groups to be reported in early
sixties.125 A perusal of Table 1 will reveal that there was no restraint in assigning trivial
names to these constituents and there are three analogues of 1, viz. 2, 3 and, margasolone
,21, five derivatives of 4, viz. 5-9, four of 10, viz. 11-14 and three of nimbione, 15. These need
to be avoided and more logical names assigned. For instance, nimbisonol (2) can easily be
called 3-hydroxy Sugiol and so on. The occurrence of nimbilicin (22) and nimolinin (24) with a
5-0H substituent is rare and that of acetyl derivatives (17 and 18) has been reported for the
first time from a natural source. The position of isopropyl substituent in margosone (20) is
curiously at C-14, contrary to biogenetic consideration. Structure elucidation in most cases
was aided by derivatisation of hydroxyl groups wherever possible and the absolute
stereochemistry was established through
(Table I). These chiefly belong to two groups, podacarpanoids and abietanoids. Sugiol (1,
12-hydroxy-13-methy1-podacarpa-8,11,13-trien-7-one) and nimbiol (4, 12-hydroxy-abieta-8,
11, 13-¬trien-7-one) were the first members of the respective groups to be reported in early
sixties.125 A perusal of Table 1 will reveal that there was no restraint in assigning trivial
names to these constituents and there are three analogues of 1, viz. 2, 3 and, margasolone
,21, five derivatives of 4, viz. 5-9, four of 10, viz. 11-14 and three of nimbione, 15. These need
to be avoided and more logical names assigned. For instance, nimbisonol (2) can easily be
called 3-hydroxy Sugiol and so on. The occurrence of nimbilicin (22) and nimolinin (24) with a
5-0H substituent is rare and that of acetyl derivatives (17 and 18) has been reported for the
first time from a natural source. The position of isopropyl substituent in margosone (20) is
curiously at C-14, contrary to biogenetic consideration. Structure elucidation in most cases
was aided by derivatisation of hydroxyl groups wherever possible and the absolute
stereochemistry was established through
| Table 1. Some physico-chemical data on phenolic Diterpenoids of pure neem oil |
Structure Name Substituents Molecular m.p. Isolated from Ref. No.
No. R1 R2 X Formula Weight (*C)
1. Sugiol Me OH H,H C16H20O2 244 297 Root bark 125
2. Nimbisonol Me OH β-OH,H C18H24O3 288 179 Stem bark 12
3. Nimbinone Me OH O C18H22O3 286 125 Stem bark 6
4. Nimbiol ipr OH H,H C18H24O3 272 250 Root bank 125
5. Nimosone ipr OH O C20H26O3 314 73 Stem bark 7
6. Methyl nimbiol ipr OMe H,H C19H26O2 286 143 Stem bark 7
7. Margocin ipr H O C20H26O2 298 134 Root bank 14
8. Margocilin ipr OH β-OH,H C20H28O3 316 127 Root bark 14
9. Margocinin CHMe OH O C20H26O4 330 144 Root bark 14
C1H2OH
10. Nimbidiol OH OH H,H C17H22O3 274 223 Root bark 97
11. Nimbionol OMe OH β-OH,H C18H24O4 304 129 Bark 141
12. Nimbionone OMe OH O C18H22O4 302 79 Bark 141
13. Demethyl nimbionol OH OH β-OH,H C17H22O4 290 135 Stem bark 12
14. Methyl nimbionone OMe OMe O C19H24O4 316 119 Stem bark 7
15. Nimbione OH Me O C18H22O3 286 103 Stem bark 6
16. Nimbonone OMe Et H,H C20H28O2 300 69 Stem bark 8
17. Nimbosodione AC OH H,H C19H24O3 300 135 Stem bark 12
18. Nimbosone AC OMe H,H C20H28O2 300 139 Stem bark 7
19. Nimbonolone OMe Et O C20H28O2 300 77 Stem bark 8
20. Margosone H ipr - C20H28O3 316 173 Stem bark 13
21. Margasolone Me H - C18H24O3 288 170 Stem bark 13
22. Nimbilicin - - - C20H24O3 312 - Root bark 9
23. Nimbocidin C19H30O2 290 - Root bark 9
24. Nimolinin C20H28O3 316 114 Root bark 11
No. R1 R2 X Formula Weight (*C)
1. Sugiol Me OH H,H C16H20O2 244 297 Root bark 125
2. Nimbisonol Me OH β-OH,H C18H24O3 288 179 Stem bark 12
3. Nimbinone Me OH O C18H22O3 286 125 Stem bark 6
4. Nimbiol ipr OH H,H C18H24O3 272 250 Root bank 125
5. Nimosone ipr OH O C20H26O3 314 73 Stem bark 7
6. Methyl nimbiol ipr OMe H,H C19H26O2 286 143 Stem bark 7
7. Margocin ipr H O C20H26O2 298 134 Root bank 14
8. Margocilin ipr OH β-OH,H C20H28O3 316 127 Root bark 14
9. Margocinin CHMe OH O C20H26O4 330 144 Root bark 14
C1H2OH
10. Nimbidiol OH OH H,H C17H22O3 274 223 Root bark 97
11. Nimbionol OMe OH β-OH,H C18H24O4 304 129 Bark 141
12. Nimbionone OMe OH O C18H22O4 302 79 Bark 141
13. Demethyl nimbionol OH OH β-OH,H C17H22O4 290 135 Stem bark 12
14. Methyl nimbionone OMe OMe O C19H24O4 316 119 Stem bark 7
15. Nimbione OH Me O C18H22O3 286 103 Stem bark 6
16. Nimbonone OMe Et H,H C20H28O2 300 69 Stem bark 8
17. Nimbosodione AC OH H,H C19H24O3 300 135 Stem bark 12
18. Nimbosone AC OMe H,H C20H28O2 300 139 Stem bark 7
19. Nimbonolone OMe Et O C20H28O2 300 77 Stem bark 8
20. Margosone H ipr - C20H28O3 316 173 Stem bark 13
21. Margasolone Me H - C18H24O3 288 170 Stem bark 13
22. Nimbilicin - - - C20H24O3 312 - Root bark 9
23. Nimbocidin C19H30O2 290 - Root bark 9
24. Nimolinin C20H28O3 316 114 Root bark 11
2D NOESY spectral analysis, showing the spatial connectivities of various H atoms. In some cases, proof by way of synthesis has been
obtained.19 It may be of interest to note that though no screening of these compounds has been done, other tricyclic diterpenes of this type
have been reported to possess a wide range of biological activities such as hypocholesterolemic, antitumor, antileukemic, antibiotic, plant
cell expansion and division inhibition and insecticidal activities.
obtained.19 It may be of interest to note that though no screening of these compounds has been done, other tricyclic diterpenes of this type
have been reported to possess a wide range of biological activities such as hypocholesterolemic, antitumor, antileukemic, antibiotic, plant
cell expansion and division inhibition and insecticidal activities.
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